The present invention generally relates to back-space editing control circuits, and more particularly to a back-space editing control circuit which carries out a control so that a rotational phase of a capstan motor is not disturbed when an operation mode of an information signal recording and reproducing apparatus is switched from a recording pause mode to a recording mode so as to perform a back-space editing.
Generally, in addition to normal recording and reproduction, various kinds of editing are performed in a video signal recording and reproducing apparatus (hereinafter simply referred to as a video tape recorder or VTR). For example, there is the so-called back-space editing for cutting unwanted parts of a television program such as commercials. When performing the back-space editing, the VTR is put into a recording pause mode during the commercials and the VTR is put back into a recording ode when the commercials are over, so that the commercials are not recorded on a magnetic tape. However, when the recording pause mode is cancelled and the VTR is put back into the recording mode to resume the recording, a discontinuity occurs between video tracks formed on the tape up to a time when the VTR is put into the recording pause mode and video tracks formed on the tape from a time when the recording is resumed. Similarly, a discontinuity occurs between a control signal recorded on the tape up to the time when the VTR is put into the recording pause mode and a control signal recorded on the tape from a time when the recording is resumed. For this reason, distortions occur in a reproduced picture and reproduced sound when such a discontinuous part on the tape is reproduced.
In order to prevent such a discontinuous part from being formed on the tape, a conventional VTR rewinds the tape by a distance corresponding to approximately thirty control pulses of the control signal recorded on the tape when the VTR is put into the recording pause mode. When the recording pause mode is cancelled and the VTR is put back into the recording mode to resume the recording, a capstan motor is controlled while the tape moves a distance corresponding to approximately twenty-five control pulses of the control signal recorded on the tape so that a regular tape moving speed is reached and video heads accurately scan over the previously recorded video tracks on the tape. The recording of the video and audio signals and the control signal is started from a time when the regular tape moving speed is reached. As a result, the video and audio signals and the control signal are recorded over the previously recorded signals on the tape for several frames of the video signal, but the previously recorded signals are only erased to such an extent that no problems are introduced from the practical point of view.
From the time when the recording pause mode is cancelled up to a time when the VTR actually assumes a stable recording state, the VTR is in the so-called assembly state. In the assemblys tate, the capstan motor is controlled so that the tape moving speed reaches the regular tape moving speed and the video heads accurately scan over the previously recorded video tracks on the tape. In the assembly state of the conventional VTR, a sampling pulse signal is obtained from the control signal reproduced from the tape or from a frequency divider reset by the reproduced control signal for frequency-dividing a capstan rotation detection pulse signal which is obtained by detecting the rotation of the capstan motor, and a sampled signal (phase error signal) is obtained by sampling a trapezoidal wave signal which is obtained from a vertical synchronizing signal of the video signal by the sampling pulse signal. The phase error signal is used to control a rotational phase of the capstan motor so that the video heads accurately scan over the previously recorded video tracks on the tape. When the assembly state is ended and the recording state is reached, a sampled signal (phase error signal) is obtained by sampling the trapezoidal wave signal by the sampling pulse signal which is obtained by frequency-dividing the capstan rotation detection pulse signal, and the rotational phase of the capstan motor is controlled by use of the phase error signal.
However, as will be described later on in the present specification in conjunction with drawings, a timing of the sampling pulse signal does not coincide with a timing of an ideal sampling pulse signal in the case where the tape moving speed is relatively small. In this case, there is a problem in that the rotational phase of the capstan motor becomes disturbed when the mode of the VTR is switched from the recording pause mode to the recording mode.